1. Field of the Invention
The invention relates to the field of computer controlled telephone equipment and in particular for equipment for communicating voice messages between coin operated telephones and telephone stations coupled through a central office switch.
2. Description of the Prior Art
Voice messaging with coin operated telephones through a central office is well known and a prior art example is shown by Axberg, "Method for Receiving and Delivering Voice Messages" U.S. Pat. No. 4,766,604 (1988). The system described in Axberg utilizes a plurality of smart pay phones connected to a privately owned central office. That is to say, pay phones must be modified to include a central processor or other logic circuitry and memory.
In Axberg a caller picks up the phone and is prompted to insert coins. After the coins are delivered, the caller's number is entered through a keypad and is stored within the smart pay phone. The number is transmitted to the central office and the smart pay phone waits for an answer detection. If the call cannot be completed, the smart pay phone issues an audio prompt and the handset is disconnected from the smart pay phone. The original call is disconnected from the trunk and the voice message center is then speed dialed through the central office by the smart pay phone. When the voice message center answers, the handset is reactivated and another prompt is produced. The caller is given the option to request the voice message center to deliver a 20 second audio message to the called station and to attempt to complete the call every 15 minutes for the next two hours. If the caller does not wish to utilize this service, he hangs up and his coins are returned from escrow. If he does wish to utilize this service, activation of the pound key releases the coin into the coin vault. The smart pay phone then transmits the called number to the voice message center through the central switching office.
The smart pay phone transmits a four digit security code to ensure that the smart pay phone is entitled to transmit voice messages to the voice message center. The security code is evaluated and if permitted, the voice message center issues a prompt to the smart pay phone asking the user to state his name and record his message. After about five seconds, a determination is made whether an audio signal is being transmitted to the voice message center.
If there is no such signal, an audio prompt is issued and the smart pay phone is disconnected. If an audio signal is being sent to the message center, the message is stored in a queue together with the transmitted called number. Thereafter, processing of the stored message and called number is completed at the voice message facility. Axberg requires substantial modification of the pay phones in order to operate within the described system.
Carter et al, "Line Interface Unit for Caller Controlled Receipt and Delivery of Voice Messages," U.S. Pat. No. 4,825,460 (1989) describes a line interface unit for controlling the receipt and delivery of voice messages over a telephone system having a voice message facility connectable to at least one calling station and a called station via a central office. The interface unit includes circuit modules, which allow it to communicate with the central office on the tip and ring lines, to translate DTMF tones from the coin phone into communication commands which stores a voice message in a voice message facility connected to the central office.
In both Axberg and Carter the coin operated telephone must be modified or provided with an interface unit which allows the telephone to communicate to the voice message facility through the central office. The need to comply with the communication protocol of the central office restricts the flexibility and communication rates which are achievable with the voice message facility.
Communication between the pay phone and the voice message facility, whether implemented by circuitry within the pay phone or in an interface line unit, must be compatible with the central office. The operation of the system as a whole is thus directly affected by any communication loads or difficulties in the central office. Thus, the signal to noise ratio realized in the system can never be better than that provided by the central office.
Software driven program execution by the voice message facility and by the pay phone must accordingly be compatible with and subject to the methodology of operation implemented within the central office. In many cases in the prior art outbound calls from the voice message facility cannot be monitored by any of the circuitry in the pay phone or line interface unit, since once the message is delivered, the voice message facility operates autonomously from the other elements within the system.
If the central switching office is overloaded, a busy or no answer condition will be returned to the pay station notwithstanding the fact that the voice message facility may otherwise have capability of handling the call.
Therefore, what is needed is a telephone communication system useable with coin operated phones which are not subject to the limitations of the prior art as discussed above and which has an architecture making it capable of performing additional communication functions not previously provided by voice message systems operating with coin operated telephones.